Heating



6 Sheets-Sheet 1 Feb}, 1939.

oz iginal Filed Feb. l5' 1924 5r a, w H a 0 f a 4 all m 4.5 m n r 9 A\ Hr? y m y My. 4 7 V f .3 W Z w a w/w 7 -1 7 7 7, 2 M a. v 1 y m INVENTOR.HMDEM/Jk 07'E55EN By S. mu mm' ATTORNEY.

w bYR-ssEN v Feb. 4, 1930. HEATING AIR AND? GASES Re. 17,577

urigmaL Files: r'o. 15, 1924 6 Sheets-Sheet 2 60 INVENTOR- W. DYRSSEN IHEATING AIR AND GASES Feb. 4, 1930.

Re. 17,577 1 6 SheetS- -S heet 3 Original Filed Feb. 15, 1924' rINVENTOR. I Mme/m? Dmsszfl A TTORNEY.

W. DYRSSEN HEATING AIR Am GASES Re. 17,577 6 Sheets-Sheet 4 Feb. 4,1930.

unginal Filed Feb. 15, 1924 If; ENTOR.

mm DYKSSE/V ATTORNEY.

i i w. DYRSSEN Feb. 4, 1930. HEATING AIR AND GASES Re. 17,577

Original Fiied Feb. 15, 1924 6 Sheets-Sheet o o, I o o 200 /98 I g V5I66 M6 I INVENTOR.' VVHLDEMIR DTKSSEIV -Reissuetl Feb. 4, 1930 UNITEDSTATES PATENT ()FIFICIE WALIlEMAR DYRSSEN, OF SHARPSBURG, PENNSYLVANIA,ASSIGNOB TO BLAW-KNOX COMPANY, OF PITTSBURGH, PENNSYLVANIA, ACORPORATION OF NEW JERSEY HEATING AIR AND GASES Original No. 1,543,909,dated June 30, 1925, Serial No. 693,021, filed February 15, 1924.Application for reissue filed June 24, i927. Serial No. 201,287.

This invention relates to the heating of air and gases and is adaptedfor'use in connection with combustion furnaces in iron and steel plantsor with boiler plants, but is, of course, not limited to such uses.

The apparatus provides means for recovering heat from waste gases byheating the combustion air for the furnace from which the waste gasesare obtained or by heating other gases or air for various otherpurposes.

There are two general types of apparatus' for preheating airnow in use,and my invention is an improvement over such conventional types ofapparatus.

The first conventlonal type comprises i a chamber provided with amultiplicity of pipes hrough which the air to be heated flows, the pipesbeing exposed on the outside to burning gases or to hot waste gases andthe heat from these gases being transferred to the air by' conduction ofthe heat through the walls of the pipes.

In some cases and in other cases the pipes are made of brick and variousrefractory materials. This gen eral type of apparatusis known in the artas a recuperator.

The second conventional type is known in ,the art as a regenerator orcheck-chamber and consists of not less than two chambers filled withbrick-work laid up in checkerwork fashion. This type is used forinstance in connection with open hearth furnaces, and

the bricks in the regenerators are heated up by gases coming from theoutgoing end of the open hearth melting chamber, and subsequently theair is passed through the chamber which has ben. prcviously heated up.In order to obtain hot air continuously, the flow of gases is reversedand the chambers are alternately heated by the waste gases and cooled bythe air passed through the chambers.

The latter type of apparatus is also used extensively in blast furnacepractice. It is ,used where gases of high temperatures are available andwhere the air is to be preheated to a comparatively high temperature.

The recuperators referred to are used for a large number of purposesboth for high and the pipes are of iron or steel low temperatures. Forlow temperature work, that is, when the gases for heating the air arerelatively cool, at the temperature,

for example, of waste gases from boilers, this must travel by conductionthrough the pipes or other heating elements. This makes the heatingelement quite ineflicient when soot or dirt is deposited on its surface.The installation is rather expensive and the maintenance is costly andtroublesome due to the necessity of keeping the heating surfaces cleanin order to maintaln. good efliciency. It is'also necessary to preventleakage between the two sides' of the heating elements, which often isvery troublesome when there is a considerable pressure differencebetween the airto be heated and the gases giving up their heat. 1

These factors have in the past prevented i the general application anduse of air heating apparatus when the hot gases are of a relatively lowtemperature.

My invention is adapted to'overco me the disadvantages of theconventional types of apparatus heretofore used, and aims to providemeans whereby the heat of waste gases of relatively low temperatures canbe utilized for heating either air or gas.

My improved apparatus is adaptedto utilize the waste gases from boilersand open hearth furnaces and especially after the waste gases from theopen. hearth furnaces have passed through waste heat boilers andhavebeen somewhat depleted of their heat units.

S'uchwaste gases have usually a temperature of from approximately 500 to700 degrees Fahrenheit.

The apparatus shown is adapted to preheat air to support combustion of'fuel in a boiler,

or to preheat ,the'air and moisture blown into the producers used formaking fuel for open hearth furnaces. .It is also adapted for proheating air for supporting combustion in open hearth furnaces, or inregenerative heat ing furnaces, the apparatus whenused in this way beingusually so placed that the air is preheated thereby it enters the usualregenerator chambers of the furnace. The apparatus can also be used forheatin the combustion air in heating furnaces o the continuous type. i

The apparatus operates on the regenerative principle, that is, the heatfrom the waste gases is stored in one part of the apparatus while theair is being heated in other parts thereof. I employ an improvedmetallic cellular structure for absorbing the heat which is so arrangedthat a very lar e heat absorption or convection surface can e.providedin a relatively small space.

I also provide means whereby the gas and air are made to alternatelytraverse different chambers at frequent time intervals which makes itunnecessary to have as large a body of heat absorbing material as wouldotherwise be necessary.

Two embodiments of the invention are i1- lustrated in the accompanyingdrawings in' which Figure 1 is a transverse vertical section through oneform of apparatus on line- 1.-I of Figure 2;

Figure 2 is a top plan thereof;

' Fi ure 3 is a fragmentary section on the line 11-111 of Figure 2;

F igure'4 is a horizontal section on a reduced scale-on line IVIV ofFigure 1;

Figure 5 is a horizontal section on the line V-V of Figure 1;

Figure 6 is an enlarged top plan showing an improved type of cellularheat exchanging structure; 1

igure'7 is a top plan of a modified embodiment of the invention, and

Figure 8 is a vertical section thereof'on line vII1 vnI of Figure 7;

Figure 9 is a diagram showing movements of reversing valves.

Referring first to F igures 1 m6, the apparatus is provided with sidewalls 10 and 12,-

end walls 14 and 16 and a top wall 18 and a bottom 20. The interior ofthe apparatus is divided by transverse walls 22 and 24, which With thewalls 14 and 16 and the walls 10 and 12 define three chambers 26,28 and30.- These plates 32 and 34.

"partition42 which divides the lower part of y ing-conduits 44 and 16.

. 'The conduit 38 communicates through a chambers are closed at the topand bottom respectively by longitudinally extending The space betweenthe plate 32 and the top 18.is divided by a longitudinally extendingpartition 36, which with the other walls defines two longitudinallyextending conduits 38 and 40. Similarly the. space between the bottom 20and the plate 34 is divided by a longitudinally extending the apparatusinto two longitudinally extendport 48 with a hot gas inlet pipe 50 and'the conduit 44 communicates'through a port 52 with a spent gas oroutlet pipe 541 Similarlv the conduit 40 communicates through a port 58with an air outlet pipe 60. The conduit 46 communicates through "a port62 with an inlet pipe 64. v

With the arrangement described, it will be seen that the longitudinallyextending conduits 38, 40, 44 and 46 are -all common to the.

several chambers 26, 28 and 30. The apparatus is designed so that thewaste gas which is to give up its heat, and the air to be heated passalternately through the several chambers 26, 28 and 30. Thatis to say,for a given interval, waste gas passes through a given chamber and thenthe supply of waste gas is cut off and the air to be heated is passedthrough the same chamber, and improved means are provided forautomatically causing this reversal at determined time intervals and thechambers 26, 28 and 30 are each provided with an improved heatexchanging cellular structure which gives a maximum heat absorbing orheat exchanging surface in a minimum amount of space.

The details of construction of the heat exchanging structure are bestshown in Figure 6. These structures vfor each heating chant her aredesignated as aavhole' in the views of the assembled structure bynumerals 27, 29' and 31. Each heat exchanging unit is made up of a greatnumber of metal plates 66 which are bent in zig-zag fashion, as bestshown in Figure 6, to form a multiplicity of substantially equilateralcells 68. The neighboring plates 66 are separated by plain or smoothplates 70 so as to give a stable construction. The corrugated and smoothplates are not united, being merely loosely nested in the chambers, itbeing unnecessary in this form of heat'exchanger to prevent leakagebetween the different cells. This loose nesting of the plates is ofadvantage because it permits of their beingmore readily and'morethoroughly cleaned. lVhen dust or soot col- 7 lects on the surface ofthe plates, the efficiency of the apparatus is reduced. The plates maybe cleaned in any desired manner, and the looseness oftheplatcs permitsof their vibrating during the cleaning step, thereby materiallyassisting in the removal of the dirt or soot. I

This zig-zag formation enables me to provide an extremely large heatingsurface in a relatively small space. For example, if the triangularsides of the cells are approximately one-half an inch in'length, Iobtain approximately 140 to 150 square feet of heating surface per cubicfoot, which is about six times as much as could be obtained by the useof one inch tubes of an ordinary recuperator. i

It will be understood that as the hot waste gas passes through theheating chambers 26, 28 or 30, they give up the greater part oftheirheat to the metallic heat exchanging elements located in these chambers.Subsequently the air is passed through the cham- V bers whereupon it isheated by contact with continuously flowing through certain of the thecellular heat exchanging members.

The arrangement is such that the gas is chambers and air to be heatediscontinuously flowing through'other chambers. The' control of this Howthrough the various chambers of the apparatus is effected by my improvedvalve arrangement to be presently described. i i

The passage of hot gas from the conduit 38, to the chambers 26, 28 and30 is controlled by separate valves 72, 74 and 76'. These valvesareloosely centered on vertically movable rods 73, and 77. Each of thesevalve rods is'i' provided with a collar 78 which when.

the rods are lifted is adapted to lift the respective valve off its seatand thereby permit the gas to flow from the conduit 38 to the corresonding chamber, the Wall 32 being provi ed with suitable openings topermit passage of the guswhen the valves are lifted.

Communication between the chambers 26, 28 and 30 and the outlet conduit44 is controlled by. valves 82, 84 and 86 which are loosely centered onthe same rods which carry the valves 72,74 and 76, The valve rods 73, 75 and 77 are each guided at the top in bushings 88 and. near'thcir lowerend in hubs 89' formed in spiders 90 secured. to the wall 34. Each ofthe rods 73, 75 and 77 carries a collar 91 adapted when thecorresponding valve rod is lifted; to lif t the corresponding valvecentered thereon.

Communication between the air conduit 40 and the chambers 26, 28 and 30is controlled by valves 92, 94 and 96, these valves being looselycentered on valve rods 93, 95'

and 97. Loosely centered on the lower part of these rods are air controlvalves 102, 104 and 106. The rods 93, 95 and 97 are each provided with acollar 108 which is adapted to lift the corresponding valve 92, 94 or 96when the respective rod is raised,and at their lower ends each of thevalve rods 93, 95 and 97 are provided with similar collars 111 arrangedto lift the valves 102, 104 or 106 when'a corresponding rod is lifted,the valve'rods .each being guided at the top by a suitable bushing 118,and near its lowerend by a hub 119 formed in the spider 120. r

The valve rods 73 and 93 are connected by chains or cables as shown inFigure 3 with the arcuate ends of a rocker arm. 122 loosely mounted on atrunnion 123 carried by a bracket 125 so that when one of the rods islifted the other red is lowered. The rods 75 and 95 are similarlyconnected to a rocker arm 124 and the rods 77 and 97 are likewiseconnected with a rocker arm 126. The arms 122, 124 and 126 are connectedrespectively by links. 128, 130 and 182 which are connected respectivelywith cranks 134, 136 and 138, which as shown in Figure 1 are set 120degrees apart, said cranks all'being carried by a common crank shaft 140having a driving gear 142 fixed thereon adapted to be driven by a pinion144 through a worm gear 146 which meshes with a,,worm 148 driven by amotor 150.

Before describing the operation, attention is called to the' fact thatthe arrows on the drawings, designated by G, represent the hot wastegases, while those designated by 9 represent the spent gases or thewaste gases which have given up their heat to the heat exchangingelements in the various chambers of the apparatus. The arrows indicatedat a represent cool or incoming air, and the arrows desigated by Arepresent the air which is heated in its passage through the cells ofthe heat exchanging units.

The hot waste gas is introduced through the pipe 50 to the longitudinalconduit 38, and with the parts in the. position shown in the drawings,the valves 72 and 76 being open, the hot waste gas passes down into thechambers 26 .and 30. In their passage through the heat exchangingelements 27 and 31 in these chambers, the waste gases contact with thevast area presented by the cellular heat exchanging units and the spentgases pass to the conduit 44 past the valves 82 and.

86 which at this time are open; the gases passing outward to a suitablestack or exhaust fan through the pipe 54.

While the hot gases were taking the course above described, air flows inthrough the pipe 64 to the conduit 46 and past the open valve 104 (thevalves 102 and 106 being closed at this time), and upward through thecellular heat exchanging unit 29 to the top of the chamber'28, theheated air flowing outpast the valve 94 to the outlet conduit 40 andthence to the hot air pipe 60.

As the shait 140 rotates slowly around (clockwise) the'valves for thethree chambers 26, 28 and 30 open and close successively andperiodically. The motion of the valves is shown in Figure 9. From thisfigure it can be seen that the valve motions during .one revolution ofthe shaft 140 can be dividedup in six periods in which the waste gasesand air flow as follows:

Period I, waste gases flow through 'chambers 26 and 30; air flowsthrough chamber 28. f Period II, waste gases flow through chamber 26;air-flows through chambers 28 and 30.

Period III, waste gases flow through charm bers 26 and 28; air flowsthrough chamber 30.

Period IV, waste gases flow through chamber'28; air flows throughchambers 26 and 30.

Period V, waste gases flow through chambers 28 and 30; air flows throughchamber 26.

Period VI, waste'gases flow through chamber 30; air flows throughchambers 26 and 28. In the diagram, one revolution of the valveoperating shaft is shown'as divided into intervals of 30 degrees byvertical lines, each period being nnmberediwith a numeral f of thefigure.

from 1 to 6 inclusive, one half of the first period being shown at theleft of the figure and the other half being shown at the right Legendshave been applied to the diagram and detailed description seems to beunnecessary, further than to say in passing, that the horizontal portionof the heavy lines indicating the valve movements represent the positionof the valve when it rests on its seat, that is to say, when it isclosed; while the curved lines represent the open movements of thevalves. The space between the broken lines parallel to the verticallines dividing the different periods in each case,

represents an interval of time during which all of the valves, that isthe gas valve and air valve for any one chamber are closed.

It will be appreciated that during such intervals there will be nocommunication between the gas and air chambers associated with thesevalves. This interval, of time is secured by the provision of means oflost motion transmitting mechanism such as the collarscarried'by thevalve rods.

As the crank shaft 140 rotates, it is clear that the several valve rods73, 75, 77-, 93, 95 and 97 are reciprocated at regular intervals.

.Bythe provision of the collars 78, 91, 108 and 111 on the valve rods, acertain amount of lost motion is provided for so that one set of,

valves, for example, say the gas .valves, re-

main seated for a short interval while the air valves are also seated. Ipossibility of passing hot waste gas directly This prevents the from thepipe 50 through any of the cham- ,bers 26, 28 or 30 to the hot air pipe60. It

will be understood that the collars may be adjustably mounted on thevalve rods so as to secure any desired dwell of the valves in theirclosed position. V

The rotating speed of shaft 140 which oper; ates the valves may varyconsiderably and maybe as high as two'or three revolutions per minuteand as low as one-fifth or onetenth revolution per minute. The heattransfertakes .place more efliciently witlrhigher speed, but at the sametime there 1s a certain amount of mixing of gases and air due to thevolume of the chambers containing the heating elements. This unavoidablemixing is less with lower speed. The wear of all moving parts and valvesmakes it also desirable to use a low shaft speed. In practice theadvantages and disadvantages must be Weighed against each other fordetermining upon the proper speed for shaft 140.

In theapparatus shown in Figures 7 and 8, the valves are all locatedabove the heating chambers, the hot gases entering through a pipe 160passing toa hot gas conduit 162 past one of the valves 16 1 to thechamber 166 through the heat exchanging unit 168 and around the wall 170through a second heat exchanger unit 172 and out past one of the openvalves 174 to a conduit 176 to the spent gas outlet pipe 178. The coolair from an inlet pipe 180 enters a conduit 182 past one of the openvalves 184: to the upper part of the heating chamber 186 through theheat pivoted on longitudinal shafts 19st and having arms 196 providedwith lugs 198 adapted to cooperate with an arm 200 which is oscillatedby a link 202 which receives its motion from a crank 204: carried on thecrank shaft 206 driven through suitable reduction gearing by a motor208.

The operation of this apparatus is very similar to that above described,and it is not thought that further description is necessary, it beingevident from the drawings that the crank shaft 206 is revolved, thevarious valves will be so manipulated that the waste gases and air willbe passed alternately through the different chambers shown in Figure '7.The lugs 198 on. the hell crank arms 196 are so positioned with respectto the arms 200 that a certain amount of lost motion provided for inorder to prevent the dii'cct passage of from the gas inlet pipe to theair outlet pipe and vice versa, or the passage of air from theair inletpipe 189 to the gas outlet pipe'178.

In the foregoing I have described an apparatus having three chambers, asthis s the minimum number at which a. continumis flow of waste gases andair can be obtained. It

is to be understood that if necessary or desirable more chambers may beused, it being merely necessary to provide one valve operating crank foreach chamber, and to so set the cranks with respect to one another thattheir angular relation is equal to 360 degrees divided by the number ofchambers or the number of cranks.

Vith three chambers there are slight fluctuations in the How of air andgas due to the variation in resistance encountered by the latter inpassing through the heat exchangers and the heatingunits locatedtherein. It is apparent that at times the gasesand air re spectivelypass through t'w'ochambers and at times through only one chamber. Thesefluctuations are minimized, however, by the variation in the opening ofthevalves.

In most cases these fluctuations are of little consequence. .However, itis to be understood that the fluctuations can be entirely eliminated byemploying a greater number of chambers. V v y Throughout the foregoingdescription and in the claims, I have referred to the terms limit theapplication to the heating of air,

that I am limited thereto as various changes in arrangement andsubstitution of equivalents. may be made by those skilled in the artwithout departing from the invention as defined in the appended claims.

What I claim is:

1. An apparatus of the class described comprising at least threechambers each having a metallic heat exchanging structure therein, hotgas and spent gas conduits common to said chambers, cool air and heatedair conduits common to said chambers, separate gas valves and a1r valvesfor the several chambers controlling the passage of gas and air to andfrom their respective chambers and a mechanism for each chamber forautomatically opening and closing its valves in a regular sequence sothat gas and air respectively are alternately passed through each ofsaid chambers, the mechanisms for different chambers being so related asto operate out of time with one another.

2. An apparatus of the class described comprising at least threetransversely extending chambers each having a metallic heat exchangingstructure therein; longitudinally extending gas inlets and gas outlets,air inlet and air outletconduits servingsaid chambers, separate valvesfor the several chambers controlling. the supply and discharge of gasand air, to and from. their respective chambers and means forautomatically opening and closing said valves in a determined sequenceso that a continuous unidirectional stream of gas and a continuousunidirectiona1 stream of air are passed through the apparatus.

3. In an apparatus of the class described, at least three chambers eachhaving a metallic heat exchanging unit therein, a gas inlet and a gasoutlet conduit common to said chambers, an air inlet and an air outletconduit common to said chambers,- separate 'valves for the severalchambers controlling the passage of gas and air to and from theirrespective chambers, and means for automatically actuating said valvesso that a unidirectional flow of gas and a unidirectional flow of air ismaintained through the apparatus.

from such 0 conduit, a gas outlet conduit, an air outlet conduit,separate gas and air valves controlling communication between thechamber and said supply and outlet conduits, a valve moving member forsimultaneously closing or opening both gas valves, a valve moving memberfor simultaneously opening or closing both air valves, and means foractuating the valve moving members, the last mentioned means being sotimed that both the gas and air valves remain closed for ashort timeinterval before their positions are reversed.

5. In an apparatus of the class described, a chamber having a heatexchanging element therein, a gas supply conduit, .an air supplyconduit, a gas outlet conduit, an air outlet conduit, separate gasvalves controlling communication between the chamber and the su pply andoutlet conduits respectively and separate air valves controllingcommunication between the chamber and said am supply'and outletconduits, valve actuating mechanism including a lost-motion devicewhereby the gas andair valves both dwell in closed position for a shortinterval before their positions are reversed.

6. In an apparatus of the class described, a chamber having a heatexchanging element therein, a gas supply conduit, an a1r supply conduit,a gas outlet conduit, an airoutlet conduit, separate gas valvescontrolling communication between the chamber and the supply and outletconduits respectively and sep arate air valves controlling communicationbetween the chamber and said air supply and outlet conduits, valveactuating mechanism.

including a constantly driven member and a lost-motion device whereby.the gas and air valves both dwell in closed position for a shortinterval before their positions are re versed.

7. In' an apparatus of the class described, at least three chambershaving a heat storage capacity, means whereby gas may be passed throughthe chambers, means whereby air may be passed through the chambers, andvalves controlling the passageof gas and air to and from the chambers,the valves bein so timed as to ensure passage of air throug 1 at leasttwo chambers during a period when an air valve for one of said twochambers is at least three 0 amber-s having a heat storagecapacity,means whereby gas ma be passed through the chambers, means w ereby airmay be passed through the chambers, and valves for each of the threechambers controlling the assage of gas and air to and hamber, an airvalve for one chamber being so timed with respect to an air valve foranother chamber that as one of said valves is opening another of saidvalves is closing.

whloh comprises admitting air to the chain 9. The method of operatin aheat regenerative device having at least t hree chambers, whichcomprises passing air through the several chambers through successiveand .overlapping time periods, passing gas through the severalv chambersthrough successive and overlapping time periods, and so timing the gasand air admission periods that air and gas are never simultaneouslyadmitted to any one chamber.

10. The method of operating a heat regenerative device having at leastthree chambers,.which comprises admitting air to the chamberssuccessively in a cycle and admit ting gas to the chambers. successivelyin a cycle, air being admitted to one chamber before being shut off fromthe chamber preceding it in the cycle of operation, and gas beingadmitted to'said' chamber before being shut off from the chamberpreceding it inthe cycle of operation, the gas being admitted to eachchamber betweenthe times when air is admitted thereto. 7

'11. The method of operating aheat regenerative device having at leastthree chambers,

hers successively in a cycle and admitting gas to the chamberssuccessively in a cycle and admitting gas to the chambers successivelyin a cycle, air being admitted to one chamber before being shut off fromthe chamber preceding it in the cycle of operation, and gas beingadmitted to said chamber before be-' ing shut cit from the chamberpreceding it.

ing the valves open or closed over an ex tended period of time, saidcontrolling means being so constructed and arranged that they areeffective for operating the chambers in overlapping ,phase relationshipwith one another so as to provide a substantially continuous supply ofheated air.

13. An apparatus of the class described comprising at least threechambers each having a heat storage capacity, and means for the severalchambers for controlling the alternate fiow of heating gases and air tobe heated through'each of the chambers, the

controlling means for the several chambers being out of time with oneanother whereby they are efi'ective for operating the chambers ,inoverlapping phase relationship with one another so as to provide a flowof air at all times through at least one chamber, and a flow of gas atall times through at least one chamber, said controlling means beingfurther so related that the flow of air through one chamber is initiatedover a time period and the flowof air through another chamber isterminated over the same time period.

14. In an apparatus of the class described, at least three chambers eachhaving a heat storage capacity,.gas inlet and gas outlet conduits commonto said chambers, air inlet and airoutlet conduits common to saidchambers, valves controlling the passage of gas and air to and from saidchambers, and means for actuating the valves, the valve actuating meansfor different-chambers being out of time with one another and beingefiective for maintaining the valves open or closed over an extendedperiod oftime, said valve actuating means being so constructed andarranged that gas and air are caused to pass alternately through each ofthe chambers with the chambers in overlapping phase relationship with 7one another so as to, provide a substantially continuous supply ofheated air.

15 In an apparatus of the class described, at least three chambers eachhaving a heat storage capacity, connections whereby heated gases andairto be heated may be passed through said chambers, valves controlling thepassage ofgas and air, and means for automatically actuating saidvalves, the valve actuating means being ofsuch character as to effectactuation of the valves for one chamber at a diiferent time than theactuation of the valves for another chamber, and the several valve meiianisms being effective for main taining the valves open or closed overan extended period of time, said valve actuating means being soconstructed and arranged that the chambers are operated in overlappingphase relationship and a substantially constant unidirectional flow ofgas and a substantially constant unidirectional flow of air ismaintained through the apparatus.

16. In an apparatus of the class described, at least three chambers eachhaving a heat storage capacity, connections whereby heating gases andair to be heated may be passed through said chambers, valves controllingthe passage of gas and air, means associated with the valves for eachchamber for actuating the same, and a common drive-means therefor, thevalve actuating means for the different chambers being out of time withone another and'being effective for maintaining the valves open orclosed over an extended period of time, saidv valve actuating meansbeing so constructed and arrangedv that the chambers are operated-inoverlapping phase relation so as to provide a substantially continuoussupply of heated air. I

17. The method of heating air which comprises passing air and gasalternately through a first chamber, passing air and gas alternatelythrbugh asecond chamber, passing air and gasalternately through a thirdchamber, initiating the flow of air through the several chambersatdifierent times, maintaining such flow through the severel chambersover time periods of suflicient len th'so that the air flow period ofone chain r overlaps the air flowperiod of another chamber, andadmitting air only or gas only .to any one chamber m at any time. p f

18.' The method of heating air which comprises passing air and gasalternately through a first chamber, passing air and gas alternatelythrough a second chamber, passing air and as alternately through a thirdchamber, initiating the flow of air through the several chambers atdifferent times, and maintain ing such flow through the several chambersover time periods of suflicient length'so that the air flow period ofone chamber overlaps the air flow period of another chamber.

' 19. The method of heating air which comprises passing air and gasalternately througha first chamber, passing air and gas alternate- 1ythrough a second chamber, passing air and gas alternating through athird chamber, air flow periods for-the several chambers being ofsubstantially equal duration and the gas flow periods for the severalchambers be-' :0 ing of substantially equal duration, and in'itiatingthe fiow of air through the several chambers at time intervals so spacedthat the air flow period of any one chamber overlaps the air flow periodof another chamber.

. as 20. The method of heating air which comprises passing air andgasalternately through a first chamber, passing air and gas alternatelythrough a second chamber, passing air and gas alternately through athird chamber,

40 the air flow periods for the several chambers being of substantiallyequal duration, and the gas flow periods for, theseveral chambers beingof substantially equal duration, initiating the flow of air through theseveral chambers at time intervals so spaced that the air flow period ofany one chamber overlaps the air flow period of another chamber, andmaintaining an idle period between the air flow and gas flow periods ofeach of the chambers.

In testimony whereof I have hereunto set m hand.

y WALDEMAR DYRSSEN.

